Origin of a paternal (13q;15q) translocation leading to dup(13q) in two half sibs.

We report on two half-sibs, a male and a female with dup(13)(q1405 leads to qter) that resulted from a der(15),t(13;15)(15qter leads to 15q25::13q1405 leads to 13qter), h+, pat. Their manifestations were similar to those with duplication of the distal half 13q. The father was a balanced de novo translocation carrier. Since the der(15) had a long secondary constriction, it was possible to trace the site of the mutation to the germ cell of the patients paternal grandmother who had this distinctive long secondary constriction in one of her normal 15 chromosomes.

[Preferential segregation of chromosome 21p- in 3 generations. Ultimate role in non-disjunction (apropos of a case of trisomy 21 in this family)]. / Segrégation préférentielle d'un chromosome 21p- dans trois générations. Rôle éventuel dans la non-disjonction (à propos d'un cas de trisomie 21 dans cette famille).

A chromosome 21p- was observed in double dose in a trisomic 21 patient; the mother and other members of her family, in three generations, were carriers of this marker chromosome. After the analysis of similar families reported in the literature, the possible role of this marker in non disjunction and its segregation during meiosis is discussed.